Repository files (latest commit first)

Filename	Latest commit message	Latest commit date
Alex Elder f099755d4c printk: drop logbuf_cpu volatile qualifier ... Pranith Kumar posted a patch in which removed the "volatile" qualifier for the "logbuf_cpu" variable in vprintk_emit(). https://lkml.org/lkml/2014/11/13/894 In his patch, he used ACCESS_ONCE() for all references to that symbol to provide whatever protection was intended. There was some discussion that followed, and in the end Steven Rostedt concluded that not only was "volatile" not needed, neither was it required to use ACCESS_ONCE(). I offered an elaborate description that concluded Steven was right, and Pranith asked me to submit an alternative patch. And this is it. The basic reason "volatile" is not needed is that "logbuf_cpu" has static storage duration, and vprintk_emit() is an exported interface. This means that the value of logbuf_cpu must be read from memory the first time it is used in a particular call of vprintk_emit(). The variable's value is read only once in that function, when it's read it'll be the copy from memory (or cache). In addition, the value of "logbuf_cpu" is only ever written under protection of a spinlock. So the value that is read is the "real" value (and not an out-of-date cached one). If its value is not UINT_MAX, it is the current CPU's processor id, and it will have been last written by the running CPU. Signed-off-by: Alex Elder <elder@linaro.org> Reported-by: Pranith Kumar <bobby.prani@gmail.com> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Petr Mladek <pmladek@suse.cz> Cc: Luis R. Rodriguez <mcgrof@suse.com> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2014-12-10 17:41:11 -08:00
..
bpf	bpf: split eBPF out of NET	2014-10-27 19:09:59 -04:00
configs	x86: Add "make tinyconfig" to configure the tiniest possible kernel	2014-08-08 16:30:24 -07:00
debug	kdb: replace strnicmp with strncasecmp	2014-10-14 02:18:25 +02:00
events	Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-12-09 20:55:37 -08:00
gcov	gcov: add ARM64 to GCOV_PROFILE_ALL	2014-10-29 16:33:14 -07:00
irq	Merge branch 'irq-irqdomain-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-12-10 09:01:01 -08:00
locking	locking/mutex: Don't assume TASK_RUNNING	2014-10-28 10:55:08 +01:00
power	PM / sleep: Fix entering suspend-to-IDLE if no freeze_oops is set	2014-11-08 22:30:05 +01:00
printk	printk: drop logbuf_cpu volatile qualifier	2014-12-10 17:41:11 -08:00
rcu	Merge branches 'torture.2014.11.03a', 'cpu.2014.11.03a', 'doc.2014.11.13a', 'fixes.2014.11.13a', 'signal.2014.10.29a' and 'rt.2014.10.29a' into HEAD	2014-11-13 10:39:04 -08:00
sched	sched_show_task: fix unsafe usage of ->real_parent	2014-12-10 17:41:09 -08:00
time	Merge branch 'timers-2038-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-12-10 10:13:28 -08:00
trace	tracing: Do not risk busy looping in buffer splice	2014-11-10 16:47:31 -05:00
.gitignore
acct.c	acct: eliminate compile warning	2014-10-09 22:26:04 -04:00
async.c	kernel/async.c: switch to pr_foo()	2014-10-09 22:26:04 -04:00
audit.c	Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-12-09 21:21:34 -08:00
audit.h	audit: reduce scope of audit_log_fcaps	2014-09-23 16:37:51 -04:00
audit_tree.c	audit: keep inode pinned	2014-11-11 14:20:22 -05:00
audit_watch.c	audit: invalid op= values for rules	2014-09-23 16:37:53 -04:00
auditfilter.c	Merge git://git.infradead.org/users/eparis/audit	2014-10-19 16:25:56 -07:00
auditsc.c	Merge git://git.infradead.org/users/eparis/audit	2014-10-19 16:25:56 -07:00
backtracetest.c
bounds.c	page-cgroup: get rid of NR_PCG_FLAGS	2014-08-08 15:57:18 -07:00
capability.c	CAPABILITIES: remove undefined caps from all processes	2014-07-24 21:53:47 +10:00
cgroup.c	Merge branch 'for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu	2014-10-10 07:26:02 -04:00
cgroup_freezer.c
compat.c	compat: nanosleep: Clarify error handling	2014-09-06 12:58:18 +02:00
configs.c
context_tracking.c	sched: stop the unbound recursion in preempt_schedule_context()	2014-10-28 10:46:05 +01:00
cpu.c	cpu: Avoid puts_pending overflow	2014-11-03 19:21:01 -08:00
cpu_pm.c
cpuset.c	sched/deadline: Ensure that updates to exclusive cpusets don't break AC	2014-10-28 10:48:00 +01:00
crash_dump.c	crash_dump: Make is_kdump_kernel() accessible from modules	2014-08-25 15:42:19 -07:00
cred.c
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c	exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent()	2014-12-10 17:41:10 -08:00
extable.c
fork.c	signal: Document the RCU protection of ->sighand	2014-10-29 10:07:18 -07:00
freezer.c	freezer: remove obsolete comments in __thaw_task()	2014-10-21 23:44:20 +02:00
futex.c	futex: Fix a race condition between REQUEUE_PI and task death	2014-10-26 16:16:18 +01:00
futex_compat.c
groups.c
hung_task.c
irq_work.c	Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu	2014-10-15 07:48:18 +02:00
jump_label.c
kallsyms.c	kernel/kallsyms.c: use __seq_open_private()	2014-10-14 02:18:16 +02:00
kcmp.c	kcmp: fix standard comparison bug	2014-09-10 15:42:12 -07:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kexec.c	kexec: remove the unused function parameter	2014-10-14 02:18:21 +02:00
kmod.c	kernel/kmod: fix use-after-free of the sub_info structure	2014-10-29 16:33:14 -07:00
kprobes.c	kprobes: Skip kretprobe hit in NMI context to avoid deadlock	2014-08-08 10:38:04 +02:00
ksysfs.c
kthread.c	kernel/kthread.c: partial revert of 81c98869fa ("kthread: ensure locality of task_struct allocations")	2014-10-09 22:25:51 -04:00
latencytop.c
Makefile	kernel: res_counter: remove the unused API	2014-12-10 17:41:04 -08:00
module-internal.h
module.c	sched, modules: Fix nested sleep in add_unformed_module()	2014-10-28 10:56:30 +01:00
module_signing.c
notifier.c
nsproxy.c	namespaces: Use task_lock and not rcu to protect nsproxy	2014-07-29 18:08:50 -07:00
padata.c
panic.c	kernel: add panic_on_warn	2014-12-10 17:41:10 -08:00
params.c	kernel/param: consolidate __{start,stop}___param[] in <linux/moduleparam.h>	2014-10-14 02:18:28 +02:00
pid.c
pid_namespace.c
profile.c
ptrace.c	exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent()	2014-12-10 17:41:10 -08:00
range.c
reboot.c	kernel: add support for kernel restart handler call chain	2014-09-26 00:00:06 -07:00
relay.c
resource.c	x86: optimize resource lookups for ioremap	2014-10-14 02:18:22 +02:00
seccomp.c	Merge branch 'x86-seccomp-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-10-14 02:27:06 +02:00
signal.c	Merge branch 'x86-mpx-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-12-10 09:34:43 -08:00
smp.c	Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu	2014-10-15 07:48:18 +02:00
smpboot.c	sched, smp: Correctly deal with nested sleeps	2014-10-28 10:56:24 +01:00
smpboot.h
softirq.c	rcu: Remove "cpu" argument to rcu_note_context_switch()	2014-11-03 19:20:34 -08:00
stacktrace.c
stop_machine.c
sys.c	x86, mpx: On-demand kernel allocation of bounds tables	2014-11-18 00:58:53 +01:00
sys_ni.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next	2014-10-08 21:40:54 -04:00
sysctl.c	kernel: add panic_on_warn	2014-12-10 17:41:10 -08:00
sysctl_binary.c	kernel: add panic_on_warn	2014-12-10 17:41:10 -08:00
system_certificates.S
system_keyring.c
task_work.c
taskstats.c	scheduler: Replace __get_cpu_var with this_cpu_ptr	2014-08-26 13:45:45 -04:00
test_kprobes.c	kernel/test_kprobes.c: use current logging functions	2014-08-08 15:57:18 -07:00
torture.c	torture: Address race in module cleanup	2014-09-16 13:41:06 -07:00
tracepoint.c
tsacct.c
uid16.c
up.c
user-return-notifier.c	scheduler: Replace __get_cpu_var with this_cpu_ptr	2014-08-26 13:45:45 -04:00
user.c
user_namespace.c	proc: constify seq_operations	2014-08-08 15:57:22 -07:00
utsname.c	namespaces: Use task_lock and not rcu to protect nsproxy	2014-07-29 18:08:50 -07:00
utsname_sysctl.c
watchdog.c	Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu	2014-10-15 07:48:18 +02:00
workqueue.c	workqueue: Use cond_resched_rcu_qs macro	2014-10-06 05:58:26 -07:00
workqueue_internal.h